CCD Performance Study for DIVA


DIVA will have two focal planes with a total of 20+2 CCDs. This web page concentrates on performance measurements of a CCD type which was selected as baseline for the DIVA mission. The page is not intended to give a general introduction into the space astrometry mission DIVA. All details about DIVA are found at the DIVA Headquarters in Heidelberg.

The DIVA focal planes

The main focal plane (FP) is covered with 20 CCD which are arranged in 5 parallel columns x 4 CCDs. 2k cols x 1k rows CCDs will be used such that each FP column is 8k pixels high and 1k pixels wide. The satellite is continously spinning so that the CCDs have to be operated in TDI mode (charge is continously moved in synchronisation with a star's movement across the focal plane). Each star will cross all 5 FP columns. The crossing time for 1 CCD (1024 rows) is about 1.5sec. The TDI clocking rate will be about 1.5msec per CCD row.

There will be 2 CCDs in the focal plane of the UV telescope.

Goals

DIVA is a space mission with the focal plane at a temperature (presumably -40C to -20C) where dark current is an issue. Experience with other space misson (e.g. Hubble Space Telecope) has shown that the detector performance will suffer from particle radiation. Dark current will increase and CTE will degrade.

Our goal is to characterize the pre-flight performance of the detectors and repeat these measurements after the CCDs are irradiated with increasing particle doses. The results will lead to requirements for the focal plane shielding on the one hand and realistic estimates of a possible sensitivity degradation of the focal plane during the mission on the other hand.

CCDs

The Marconi CCD42-20 with 2048 columns by 1024 rows is baseline for DIVA.
Under study are:

Location

Tests are performed in parallel at two german institutes.

Funding

This study is funded by the Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR).
 
 
 
 

CCD performance


 

Klaus Reif, 17.05.2002